Diagnostic Strategy

Diagnosis of an electronically-controlled automatic transmission is simple using the following procedures. One of the most important things to remember is that there is a definite procedure to follow. Follow the procedures as written to avoid missing critical components or steps. By following the diagnostic sequence, the technician will be able to diagnose and repair the concern the first time.

Note: Do not take any shortcuts or assume that critical checks or adjustments have already been made.

Note: Follow the procedures as written to avoid missing critical components or steps.

To correctly diagnose a concern, have the following publications available:
- Technical Service Bulletins (TSBs).
Use the Diagnostic Flow Chart as a guide and follow the steps as indicated.

Preliminary Inspection
- Know and understand the customer concern.
- Verify the concern by operating the vehicle.
- Check the fluid level and condition.
- Check for non-factory add-on items.
- Check shift linkage for correct adjustment.
- Check TSBs regarding the concern.

Diagnostics
Carry out on-board diagnostic procedures Key On Engine Off (KOEO) and Key On Engine Running (KOER).
- Record all Diagnostic Trouble Codes (DTCs).
- Repair all non-transmission codes first.
- Repair all transmission codes second.
- Erase all continuous codes and attempt to repeat them.
- Repair all continuous codes.
- If only pass codes are obtained, proceed to Diagnosis by Symptom.Symptom Related Diagnostic Procedures
Follow the Diagnostic Flow Chart sequence to diagnose and repair the concern the first time.